1. Field of the Invention
The present invention relates to a method for enzymatic determination of 1,5-anhydroglucitol, a reagent for use in the method, novel trehalase which is suitable for use in the method for enzymatic determination of 1,5-anhydroglucitol, and a process for producing the novel trehalase. The determination of the 1,5-anhydroglucitol concentration is useful in diagnosis of diabetes.
2. Description of Related Art
It is known that 1,5-anhydroglucitol is present in human cerebrospinal fluid and blood plasma and that the level of 1,5-anhydroglucitol changes in patients of some diseases, especially diabetes, and thus it is important as a diagnostic marker for diabetes. Previous methods for quantitatively determining 1,5-anhydroglucitol include a method using a special analytical instrument such as gas chromatography, a method using an enzyme which specifically oxidizes 1,5-anhydroglucitol (Japanese Published Unexamined Patent Application No. 79780/87), and a method which comprises converting substances such as glucose in a sample to other substances by using various enzymes, and then determining the amount of 1,5-anhydroglucitol remaining in the sample by using pyranose oxidase or L-sorbose oxidase (Japanese Published Unexamined Patent Application No. 185397/88).
Generally, instrumental analyses such as liquid chromatography and gas chromatography involve complicated pretreatment of samples, requires expensive special instruments, and is time-consuming; therefore, this method is not suitable for the analysis of a large number of samples. In the method using an enzyme which specifically acts on 1,5-anhydroglucitol, it is not easy to prepare the enzyme and to lead to an appropriate detection system. The method using pyranose oxidase has the defect that the substrate specificity of pyranose oxidase is insufficient.